A set of 25 B6.C congenic strains of mice, which were derived from B6 (C57BL/6By) and BALB/cBy inbred strains for the purpose of isolating histocompatibility genes, will be used to identify the genes that effect small changes in morphology of the skeleton. Skeletons from the congenic strains and from the B6 background strain will be prepared by papain digestion, bones will be measured under a microscope to obtain 50 metric traits, and the data will be reduced to a set of uncorrelated variates (axes of a multidimensional (hyper) space by canonical variate analysis of pooled dispersion matrices). A significant difference (distance in the derived hyperspace) between a congenic strain and the background strain will signify the presence of a gene of interest. The direction in which the congenic strain is located away from the background strain in the hyperspace will uniquely define the gene effect. Whether the histocompatibility gene for which each congenic strain was originally constructed, or another gene, is the one with the morphogenetic effect, will be tested by backcrossing each indicated congenic strain to the background strain. Skin graft tests in the progeny will reveal whether association with the histocompatibility gene is maintained, thereby providing evidence on pleiotropic effects on histocompatibility genes on morphology. Crosses between indicated congenic strains and B6 will be made to reveal the dominance-recessivity and epistatic nature of gene expression.